1. Field of the Invention
The present invention relates to a method of patterning an organic macromolecular film such as a photoresist.
2. Description of the Background Art
FIGS. 17 to 19 are cross-sectional views showing a conventional method of patterning a photoresist which is formed on a semiconductor substrate having an uneven surface. The method will be discussed hereinafter with reference to FIGS. 17 to 19.
Initially, a semiconductor substrate 1 which has concave portions formed on the surface thereof is coated all over with a negative photoresist 2, as shown in FIG. 17.
As shown in FIG. 18, shade masks 3 are disposed in regions corresponding to the concave portions above the semiconductor substrate 1. Light 4 is directed from above the shade masks 3 to the photoresist 2 to polymerize (expose) only part of the photoresist 2 above which the shade masks are absent and which is formed on the smooth surface of the semiconductor substrate 1.
The semiconductor substrate 1 is immersed in an appropriate solvent, so that only part of the photoresist 2 which is on the concave portions and is not illuminated is removed, and the part of the photoresist 2 which is polymerized by the illumination remains unremoved.
By forming the photoresist 2 only on the region other than the concave portions of the semiconductor substrate 1 by the use of the shade masks 3, a diffusion processing can be performed only on the concave portions of the semiconductor substrate 1. An example of the processing performed on the concave portion of the semiconductor substrate 1 is disclosed in FIG. 5 of Japanese Patent Application Laid-Open No. 62-160776.
The conventional method of the type in which the photoresist 2 is patterned on the region other than the concave portions of the semiconductor substrate has been carried out by disposing the shade masks 3 above the semiconductor substrate 1 and directing light from above the shade masks 3 to the photoresist 2. In this method, however, it is difficult to accurately dispose the shade masks 3 in the regions corresponding to the concave portions of the semiconductor substrate 1. There has been a problem that the organic macromolecular film cannot be accurately patterned in corresponding relation to the concave portions.
Another problem is that, when the light 4 enters under the shade masks 3 as shown in FIG. 20, part of the photoresist 2 which should not be illuminated is polymerized so that the pattern accuracy of the photoresist 2 remarkably deteriorates.